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                [Poi1998]Flat broken lines                </h1>
                <p>时间限制：1s&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;  空间限制：128MB</p>			</div>
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                                <h3>题目描述</h3><p><p><span style="font-size: medium">给定二维直角坐标系。我们要求一条折线只能从左边到右边一笔画过去，并且折线的每一段和x轴的夹角在[-15&deg;, 15&deg;]之间。一条满足上述要求的折线被称为：平直折线。</span></p>
<p><span style="font-size: medium">给定坐标系上的n个格点，最少需要画多少条平直折线才能覆盖所有的点呢？</span></p>
<p><span style="font-size: medium">例如：</span></p>
<p><span style="font-size: medium">&lt;img src=&quot;</span><a href="http://main.edu.pl/en/images/OI5/lam.gif"><span style="font-size: medium">http://main.edu.pl/en/images/OI5/lam.gif</span></a><span style="font-size: medium">&quot; alt=&quot;example&quot; /&gt;</span></p>
<p><span style="font-size: medium">上图有6个点：(1, 6), (10, 8), (1, 5), (2, 20), (4, 4), (6, 2)，最少需要3条平直折线。</span></p>
<p></p></p><hr/><h3>输入格式</h3><p><p><span style="font-size: medium">第一行，1个正整数：点数n (&lt;= 30000)<br />
下面n行：坐标(x, y) ，(0 &lt;= x, y &lt;= 30000)</span></p>
<p></p></p><hr/><h3>输出格式</h3><p><p><span style="font-size: medium">最少需要多少条平直折线</span></p>
<p></p></p><hr/><h3>样例输入</h3><pre>6
1 6
10 8
1 5
2 20
4 4
6 2

</pre><hr/><h3>样例输出</h3><pre>
3
</pre><hr/><h3>提示</h3><p>没有写明提示</p><hr/><h3>题目来源</h3><p>没有写明来源</p>
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